Methods of forming dielectric layers and methods of forming capacitors

ABSTRACT

Methods of forming dielectric layers and methods of forming capacitors are described. In one embodiment, a substrate is placed within a chemical vapor deposition reactor. In the presence of activated fluorine, a dielectric layer is chemical vapor deposited over the substrate and comprises fluorine from the activated fluorine. In another embodiment, a fluorine-comprising material is formed over at least a portion of an internal surface of the reactor. Subsequently, a dielectric layer is chemical vapor deposited over the substrate. During deposition, at least some of the fluorine-comprising material is dislodged from the surface portion and incorporated in the dielectric layer. In another embodiment, the internal surface of the reactor is treated with a gas plasma generated from a source gas comprising fluorine, sufficient to leave some residual fluorine thereover. Subsequently, a substrate is exposed within the reactor to chemical vapor deposition conditions which are effective to form a dielectric layer thereover comprising fluorine from the residual fluorine.

CROSS REFERENCE TO RELATED APPLICATION

This is a Continuation of U.S. patent application Serial No. 09/032,765,filed Feb. 28, 1998, and titled “Methods of Forming Dielectric Layersand Methods of Forming Capacitors”, now U.S. Pat. No. 6,147,011.

TECHNICAL FIELD

This invention relates to methods of forming dielectric layers and tomethods of forming capacitors.

BACKGROUND OF THE INVENTION

Dielectric material layers are essential components in integratedcircuitry capacitors, and are typically interposed between two capacitorplates. Capacitors are used in memory circuits, such as dynamic randomaccess memory (DRAM) arrays.

As device dimensions continue to shrink, an important emphasis is placedon maintaining, and in some instances, increasing a capacitor's abilityto store a desirable charge. For example, a capacitor's charge storagecapability can be increased by making the capacitor dielectric thinner,by using an insulator with a larger dielectric constant, or byincreasing the area of the capacitor. Increasing the area of a capacitoris undesirable because the industry emphasis is on reducing overalldevice dimensions. On the other hand, providing a thinner capacitordielectric layer and/or using an insulator with a larger dielectricconstant can present problems associated with current leakage, such asthat which can be caused by Fowler-Nordheim Tunneling. Current leakagecan significantly adversely impact the ability of a capacitor to store acharge.

This invention grew out of needs associated with providing methods offorming dielectric layers having sufficiently high dielectric constants.This invention also grew out of needs associated with providing methodsof forming capacitor constructions which have desirable charge storagecharacteristics, and reduced current leakage.

SUMMARY OF THE INVENTION

Methods of forming dielectric layers and methods of forming capacitorsare described. In one embodiment, a substrate is placed within achemical vapor deposition reactor. In the presence of activatedfluorine, a dielectric layer is chemical vapor deposited over thesubstrate and comprises fluorine from the activated fluorine. In anotherembodiment, a fluorine-comprising material is formed over at least aportion of an internal surface of the reactor. Subsequently, adielectric layer is chemical vapor deposited over the substrate. Duringdeposition, at least some of the fluorine-comprising material isdislodged from the surface portion and incorporated in the dielectriclayer. In another embodiment, the internal surface of the reactor istreated with a gas plasma generated from a source gas comprisingfluorine, sufficient to leave some residual fluorine thereover.Subsequently, a substrate is exposed within the reactor to chemicalvapor deposition conditions which are effective to form a dielectriclayer thereover comprising fluorine from the residual fluorine.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a schematic diagram of a chemical vapor deposition reactor inaccordance with one aspect of the invention.

FIG. 2 is a view of a portion of the reactor.

FIG. 3 is a view of a portion of the reactor.

FIG. 4 is a schematic diagram of another reactor in accordance withanother aspect of the invention.

FIG. 5 is a view of the FIG. 1 reactor at a processing step inaccordance with one aspect of the invention.

FIG. 6 is a diagrammatic side sectional view of a portion of a waferfragment, in process, in accordance with one aspect of the invention.

FIG. 7 is a view of the FIG. 6 wafer fragment at a different processingstep.

FIG. 8 is a graph of capacitance versus leakage current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

Referring to FIG. 1, a chemical vapor deposition reactor is showngenerally at 10. Reactor 10 can comprise any suitable reactor which iscapable of processing substrates as described below. The illustratedreactor includes a pair of electrodes 12, 14 which can be biased by anRF source 16. RF source 16 can be used, in one implementation, togenerate a gas plasma within the reactor. Various other reactor typesand designs, some of which can be used in connection with variousaspects of the invention, are described in a text by Lieberman andLichtenberg, entitled Principles of Plasma Discharges and MaterialsProcessing, the disclosure of which is incorporated by reference.

Reactor 10 is typically used to chemical vapor deposit various layersover a substrate (not shown) and can include a source 18 through whichvarious precursor gases are provided and processed. Such gases can alsobe provided through an electrode, such as electrode 12.

Referring to FIGS. 1-3, reactor 10 includes an internal surface 20 whichdefines a processing chamber in which processing takes place. Theillustrated reactor is depicted at a processing point prior to placementof a substrate therein. A halogen-comprising material, preferably afluorine-comprising material 22 (FIG. 2), 24 (FIG. 3), is formed over atleast a portion of surface 20. In a most preferred aspect,halogen-comprising material comprises activated fluorine. By “activated”is meant that the material can include ions, radicals, electrons, andother excited species having lifetimes which are influenced by variousfactors.

One way of providing the activated fluorine material 22, 24 is togenerate a fluorine-comprising gas plasma having activated fluorinetherein. Such plasma can be generated by introducing afluorine-comprising source gas, such as NF₃, into the reactor, andsubjecting the source gas to processing conditions which are effectiveto form the gas plasma. Such processing conditions can include, in thereactor illustrated in FIG. 1, subjecting the source gas to suitable RFenergy sufficient to form the plasma. Accordingly, internal surface 20is treated with the gas plasma prior to introduction of a substratetherein. Such treatment effectively leaves residual activated fluorineover surface 20 in the absence of a substrate. Accordingly in thisexample, the substrate is not exposed to the gas plasma. Coverage ofsurface 20 by the activated fluorine can be non-uniform, as shown inFIG. 3. Preferably, at least some of the residual activated fluorine ispresent during the chemical vapor depositing of a dielectric layer whichis described just below.

In this example, and because the substrate is not present in the reactorduring formation of the gas plasma, the gas plasma is formed away fromthe substrate. Accordingly, the reactor is preferably substantially, ifnot completely, plasma-free during the depositing of the dielectriclayer. By “substantially” is meant that it can be possible, in somereactor types, for plasma to exist in the reactor substantially remoteof the substrate. Such is more likely to occur with the reactor designillustrated in FIG. 4. There, a reactor 26 includes a remote plasmasource 28 operably coupled therewith. Source 28 is preferably one whichis capable of generating a gas plasma, from the fluorine-comprisingsource gas, which is subsequently flowed into reactor 26. In this way, agas plasma is formed away from any substrate which might be present inFIG. 4. Remote plasma processing and apparatuses for conducting suchprocessing are described in U.S. Pat. No. 5,180,435, entitled “RemotePlasma Enhanced CVD Method and Apparatus for Growing an EpitaxialSemiconductor Layer”, the disclosure of which is incorporated byreference. In the illustrated example, only electrodes 12 a, 14 a areshown. A substrate is not specifically depicted in the FIG. 4 example. Asubstrate could, however, be present in reactor 26 during formation of,and subsequent flowing of the activated fluorine from remote plasmasource 28.

Referring to FIG. 5, a substrate 30 is placed within reactor 10, andpreferably after the internal walls of the reactor have been pretreatedwith the fluorine-comprising gas plasma. In the presence of activatedfluorine within the reactor, the substrate is exposed to conditionswhich are effective to chemical vapor deposit a dielectric layer overthe substrate which comprises fluorine from the activated fluorine.Processing conditions under which dielectric layers can be depositedinclude using liquid chemical precursors including tantalumpentaethoxide (TAETO) or tantalum tetraethoxide dimethylaminoethoxide(TAT-DMAE), at temperatures from between about 400° C. to 500° C., andpressures from between about 30 mTorr to 30 Torr. Other precursors suchas BST precursors, e.g. M(thd)₂, where M is either Ba or Sr, attemperatures from between about 500° C. to 650° C., and pressures frombetween about 30 mTorr to 30 Torr, can be used.

Preferably, the dielectric layer has a dielectric constant or “k” valuewhich is greater than about 6. Exemplary materials for the dielectriclayer can include silicon nitride (“k” value of around 7), tantalumpentoxide (Ta₂O₅)(“k” values ranging from about 10-25), BST (“k” valuesranging from about 100 to 1000 or greater). The dielectric layerpreferably comprises less than about 10% fluorine, by weight. Morepreferably, the dielectric layer comprises between about 0.001% and 10%fluorine, by weight.

Referring to FIGS. 6 and 7, a capacitor forming method is describedrelative to a substrate 32. Such can comprise any suitable substrateover which a capacitor is to be formed. An exemplary capacitor formed inconnection with dynamic random access memory circuitry includes asubstrate comprising insulative materials, such as borophosphosilicateglass. A first capacitor plate 34 is formed over substrate 32,typically, by chemical vapor deposition of polysilicon. In the presenceof activated fluorine, as described above, a dielectric layer 36 ischemical vapor deposited over first capacitor plate layer 34. A secondcapacitor plate layer 38 is formed over dielectric layer 36 to provide acapacitor construction.

In one reduction-to-practice example, an Applied Materials 5000processing chamber was cleaned, prior to introduction of a substratetherein, with a remote NF₃ plasma under the following processingconditions: 1500 sccm of NF₃, 1800-3200 watts at around 2 Torr for aduration of about 100 seconds. After the plasma clean, a semiconductorwafer was placed in the chamber and a dielectric layer, such as thoselayers described above, was formed over the wafer. The followingconditions were used: temperature of around 475° C. with 300 sccmTAT-DMAE, 250 sccm of O₂, spacing of 350 mils, and a pressure of 1 Torr.

FIG. 8 illustrates, for the reduction-to-practice example, a graph ofcapacitance versus leakage current for two areas over the wafer. Datapoints, collectively grouped at 40, correspond to capacitance andleakage current measurements taken at or near the center of the wafer.Data points, collectively grouped at 42, correspond to capacitance andleakage current measurements taken at or near the edge of the wafer. Asa consequence of the chamber geometry of the Applied Materials 5000chamber, more residual fluorine-comprising material (e.g. activatedfluorine), is prevalent at the edge of the wafer. Hence, the edge of thewafer is more influenced by the above-described treatment than otherwafer portions such as those at or near the center of the wafer.Plotting capacitance versus leakage for the two areas indicates that thecapacitance achieved at or near the edge of the wafer (i.e.,corresponding to data points 42) is generally greater than thecapacitance at or near the center of the wafer (i.e., corresponding todata points 40). In addition, data points 42 constitute wafer areasgenerally having less leakage current for a given capacitance than thosedefined by data points 40. Accordingly, for some of the data points, anoverall increase in capacitance was observed with a lowering of theleakage current. In addition, the deposition rate of the dielectriclayer was observed to increase in the presence of the residual activatedfluorine.

Accordingly, the methods described above permit dielectric layers havingincreased dielectric constants to be formed. Such permits capacitorshaving reduced dimensions to be formed with desirable charge storagecharacteristics.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of forming a dielectric layercomprising: providing activated fluorine over an interior surface of areactor; and chemical vapor depositing a dielectric layer over asubstrate placed within the reactor, the dielectric layer comprisingfluorine from the activated fluorine.
 2. The method of claim 1, furthercomprising providing activated fluorine over an interior surface of thereactor prior to placing the substrate within the chemical vapordeposition reactor.
 3. The method of claim 2, wherein providingactivated fluorine over the interior surface of the reactor comprisesproviding activated fluorine from a gas plasma.
 4. The method of claim1, further comprising generating a gas plasma comprising the activatedfluorine, the substrate not being exposed to the gas plasma.
 5. Themethod of claim 1, further comprising generating a gas plasma comprisingthe activated fluorine, the gas plasma being remote from the reactor. 6.The method of claim 1, wherein chemical vapor depositing a dielectriclayer comprises depositing a dielectric layer having a dielectricconstant greater than about six.
 7. A method of forming a dielectriclayer comprising: forming a fluorine-comprising material over at leastan interior surface portion of a chemical vapor deposition reactor; andchemical vapor depositing a dielectric layer over a substrate within thereactor and dislodging at least some of the fluorine-comprising materialfrom the surface portion to incorporate at least some fluorine of thefluorine-comprising material in the dielectric layer.
 8. The method ofclaim 7, wherein forming the fluorine-comprising material comprisesforming activated fluorine over the surface portion.
 9. The method ofclaim 7, wherein forming the fluorine-comprising material comprisesgenerating a fluorine-comprising gas plasma having activated fluorinetherein which is formed over the surface portion.
 10. The method ofclaim 7, wherein forming the fluorine-comprising material comprisesgenerating a fluorine-comprising gas plasma remote from the chemicalvapor deposition reactor, the gas plasma having activated fluorinetherein, and providing at least some of the activated fluorine from thegas plasma over the surface portion.
 11. The method of claim 7, whereinforming the fluorine-comprising material comprises generating a gasplasma from a source gas comprising NF₃, the plasma having activatedfluorine therein which is formed over the surface portion.
 12. Themethod of claim 7, wherein forming the fluorine-comprising materialcomprises generating a gas plasma from a source gas consisting of NF₃,the plasma having activated fluorine therein which is formed over thesurface portion.
 13. The method of claim 7, wherein forming thefluorine-comprising material comprises generating a gas plasma from asource gas comprising NF₃, the gas plasma being remote from the chemicalvapor deposition reactor, the gas plasma having activated fluorinetherein, and providing at least some of the activated fluorine from thegas plasma over the surface portion.
 14. The method of claim 7, whereinchemical vapor depositing a dielectric layer comprises depositing adielectric layer comprising tantalum pentoxide.
 15. A method of forminga dielectric layer comprising: treating an internal surface of achemical vapor deposition reactor with a gas plasma generated from asource gas comprising NF₃ sufficient to leave some residual fluorinethereover; and exposing a substrate within the reactor to chemical vapordepositing conditions effective to form the dielectric layer thereoverto comprise fluorine from the residual fluorine.
 16. The method of claim15, wherein at least some of the residual fluorine comprises activatedfluorine.
 17. The method of claim 15, wherein at least some of theresidual fluorine comprises activated fluorine which is present duringthe chemical vapor depositing of the dielectric layer.
 18. The method ofclaim 15, wherein exposing the substrate to chemical vapor depositingconditions comprises doing so in the absence of the gas plasma.
 19. Themethod of claim 15, wherein exposing a substrate within the reactor tochemical vapor depositing conditions effective to form a dielectriclayer thereover comprises exposing the substrate to chemical vapordpositing conditions effective to form the dielectric layer thereover tocomprise a material having a dielectric constant greater than about six.20. The method of claim 15, wherein exposing a substrate within thereactor to chemical vapor depositing conditions effective to form adielectric layer thereover comprises exposing the substrate to chemicalvapor depositing conditions effective to form the dielectric layerthereover to comprise tantalum pentoxide.
 21. The method of claim 15,wherein exposing a substrate within the reactor to chemical vapordepositing conditions effective to form a dielectric layer thereovercomprises exposing the substrate to chemical vapor depositing conditionseffective to form the dielectric layer thereover to comprise less thanabout 10% by weight of fluorine.
 22. The method of claim 15, whereinexposing a substrate within the reactor to chemical vapor depositingconditions effective to form a dielectric layer thereover comprisesexposing the substrate to chemical vapor depositing conditions effectiveto form the dielectric layer thereover to comprise between about 0.001%and 10% by weight of fluorine.
 23. A method of forming a capacitorcomprising: treating an internal surface of a chemical vapor depositionreactor with a gas plasma generated from a source gas comprisingfluorine sufficient to leave some residual activated fluorine thereover;after said treating, placing a substrate including a first capacitorplate layer within the chemical vapor deposition reactor; and chemicalvapor depositing a dielectric layer over the first capacitor plate layercomprising at least some fluorine from the activated fluorine over thesubstrate.
 24. The method of claim 23, further comprising forming asecond capacitor plate layer over the dielectric layer.
 25. The methodof claim 23, wherein treating an internal surface comprises forming agas plasma from a fluorine-comprising source, the gas plasma having atleast some activated fluorine therein which is provided within thereactor.
 26. The method of claim 25, wherein the gas plasma is formedaway from the substrate.
 27. The method of claim 23, wherein treating aninternal surface comprises: providing a remote plasma source operablycoupled with the reactor; in the remote plasma source, generating thegas plasma from a fluorine-comprising source gas, the plasma includingactivated fluorine; and flowing activated fluorine from the gas plasmainto the reactor.
 28. The method of claim 27, wherein the substrate isnot exposed to the gas plasma.
 29. The method of claim 27, wherein thereactor is substantially plasma-free during the depositing of thedielectric layer.
 30. The method of claim 27, wherein depositing thedielectric layer comprises depositing the dielectric layer when thereactor is plasma-free.
 31. The method of claim 27, wherein generating agas plasma comprises generating a gas plasma from a gas comprising NF₃.32. The method of claim 23, wherein the dielectric layer comprisesmaterial having a dielectric constant greater than about six.
 33. Amethod of forming a dielectric layer in a chemical vapor depositionreactor comprising: providing activated halogen species over an interiorsurface of the reactor and a substrate within the reactor; and chemicalvapor depositing a dielectric layer over the substrate comprisingmaterial from the activated halogen species.
 34. The method of claim 33,further comprising providing activated halogen species over the interiorsurface of the reactor prior to placing the substrate within thechemical vapor deposition reactor.
 35. A method of forming a dielectriclayer in a chemical vapor deposition reactor comprising: generating afluorine-comprising gas plasma having activated fluorine therein;disposing some of the activated fluorine over at least a surface portionof an interior of the reactor; and chemical vapor depositing adielectric layer over a substrate within the reactor and dislodging atleast some of the activated fluorine from the surface portion toincorporate at least some fluorine of the activated fluorine in thedielectric layer.
 36. The method of claim 35, wherein generating afluorine-comprising gas plasma comprises generating afluorine-comprising gas plasma remote from the chemical vapor depositionreactor, the gas plasma having activated fluorine therein, and providingat least some of the activated fluorine from the gas plasma over thesurface portion.
 37. The method of claim 35, wherein the dielectriclayer comprises tantalum pentoxide.
 38. A method of forming a dielectriclayer using a chemical vapor deposition reactor comprising: generating afluorine-comprising gas plasma having activated fluorine therein; sdisposing some of the activated fluorine over at least a surface portionof an interior of the reactor; after disposing, introducing a substrateinto the reactor; and chemical vapor depositing a dielectric layercomprising tantalum pentoxide over a substrate within the reactor anddislodging at least some of the activated fluorine from the surfaceportion to incorporate at least some fluorine of the activated fluorinein the dielectric layer.
 39. A method of forming a dielectric layercomprising: providing a chemical vapor deposition reactor having aninternal surface; treating the internal surface with a gas plasmagenerated from a source gas comprising NF₃ sufficient to leave someresidual activated fluorine thereover; and after said treating, exposinga substrate within the reactor to chemical vapor depositing conditionsin the absence of the gas plasma effective to form a dielectric layerthereover comprising fluorine from the residual fluorine, wherein atleast some of the residual fluorine comprises activated fluorine whichis present during the chemical vapor depositing of the dielectric layerand wherein the dielectric layer comprises between about 0.001% and 10%by weight of fluorine.
 40. The method of claim 39, wherein thedielectric layer comprises a material having a dielectric constantgreater than about six.
 41. The method of claim 39, wherein thedielectric layer comprises tantalum pentoxide.